ATLANTA — U.S. and international health officials now believe a flu-like illness from Asia that has sickened hundreds of people may actually be a new, virulent version of an old enemy: the common cold virus.
Officials with the Centers for Disease Control and Prevention said tests revealed traces of a form of microbe known as a coronavirus in the tissue of people infected with the mysterious illness called "severe acute respiratory syndrome," or SARS.
There are three known varieties of the coronavirus, but the CDC said Monday the culprit in the Asian outbreak appears to be genetically different and probably represents a fourth type.
"There's very strong evidence to support coronavirus" as the cause, said CDC director Dr. Julie Gerberding. "If (coronavirus) is not the entire cause of SARS, it at least contributes to it."
But she cautioned that more testing is needed — by the CDC and international labs — before experts can be certain. No approved treatment exists either for SARS or what could be the illness' cousin, the common cold.
SARS first gained attention in Hong Kong, Singapore and Vietnam, where it has spread among health workers. Health authorities say it appears to spread from close contact, primarily through nasal fluids by coughing or sneezing. Nearly 460 people have been sickened worldwide, and 17 have died.
In the United States, 39 people in 18 states likely have been made ill by SARS.
Most of those suspected cases — 32 people — are believed to have acquired it from recent travel to Asia. Seven others were health workers or family members who had close contact with those affected, Gerberding said.
The Geneva-based World Health Organization issued a worldwide travel alert March 15 warning people to watch for symptoms after traveling to places where the disease has appeared. The WHO also got its network of 11 labs around the world working to find the cause and treatment of the disease.
David Heymann, head of communicable diseases at WHO, said Tuesday he was satisfied that the containment policy in Singapore and Vietnam was proving successful. The organization also has sent a five-man team to China with hopes of going to Guangdong, the southern province with an outbreak of atypical pneumonia that has similar symptoms to SARS.
Finding a cause could lead to a treatment for the disease and a diagnostic test that could identify it in patients, said Dr. Edward Chapnick, infectious diseases director of Maimonides Medical Center in Brooklyn, N.Y.
Last week, the World Health Organization thought a possible cause was paramyxovirus — the family of viruses that causes measles and mumps. CDC officials looked for paramyxovirus during their testing, but instead found evidence that a new form of coronavirus was the cause.
The CDC found that SARS victims develop an immune system response to coronavirus during the course of their illness. The virus also was found in kidney specimens and victims' lung tissue.
Besides colds, coronavirus can cause respiratory illnesses that sometimes lead to bronchitis and pneumonia. Other forms can be much more dangerous, causing significant lower respiratory tract illnesses among animals, said Dr. Frederick Hayden, clinical virologist for the University of Virginia Health System.
"If this is coronavirus it certainly would be a novel one, different than how the recognized human coronaviruses behave," Hayden said. "But, if confirmed, it's a very important step forward in trying to . . . reunderstand its epidemiology and to devise methods for coping for it."
The Defense Department is testing the virus against all known antiviral drugs to see if any are effective, Gerberding said. There has been progress with antivirals against other respiratory viruses, particularly influenza, and some of those drugs have been effective in studies against some coronaviruses.
Meanwhile, fears of the disease seemed to spread in Asia: Singapore quarantined more than 700 people who may have been exposed to the disease, threatening them with fines; Hong Kong officials met to draw up health guidelines for everything from restaurants to bus systems in an attempt to slow its spread.
On the Net: CDC: www.cdc.gov/ncidod/sars